What is a "156C bur" and where is it used? - 17 photos

 This tutorial essay might look like a repeat to many people, but I'm writing about the many aspects of this very common bur. I missed just one simple word, "IMPORTANT".

These burs have one thing in common, they will make your setting job exciting. They must create a means of holding any stone against the claw, without endangering it.

  These burs come in many sizes, as seen in my collection of '156C' burs. The letter 'C' refers to CARBIDE, which the burs are made of.

 The burs come in two measured sizes "70" and "90" degree angles. You as a jeweller, must specify to your tool supplier which size of bur-angle you require.

  As I collect multiple sizes of "156C" burs, the burs must always be at hand-reach rather than being at random on my bench. 

 I use these burs solely for "Gypsy & Channel Setting". These burs have finely contoured teeth that will cut into the metal without risking any damage to the stone.

 Here are 5 stones that are 'almost' the same size in the channel ring. There must never be deep grooves made for the stones, only a slight indentation for the Girdle. 

  Before any modification for the thick Girdle, I will use this "156C" bur to prepare for the setting of the stone.

 

 I have 2 pallets of 156C burs, I have one pallet for the small-sized burs and the second pallet for the larger sizes. You can see the many sizes of the mini-sized burs. 

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                             Examples of the many uses of a "156C" bur.

 Imagine using the HSS (High-Speed Steel) bur for this multitude of mini-claws. As this is a totally different setting project, great care is paramount and 100% essential when setting these stones. 

 "MISTAKES, OR ERRORS" ARE NOT IN OUR  GEMSETTING VOCABULARY.

 Here are diamond-encrusted letters in claws-diamonds. Gentle drilling in getting the stones set is a prime example of using burs with the greatest care. "Slow speed of drilling" is of the utmost importance.

  

 When you are preparing to set a "Gypsy-Setting", I suggest only drilling 3 or 4 times around the hole and into the metal. "SPEED KILLS" drill the hole slowly.

  

 How deep into the metal should you use this bur? The answer is important as the bur shaft is the clue in preparing the bearing cut.

 The 'bur depth' must not exceed the 'edge of the teeth from the shaft of the bur'. This is the only rule I can guide you with.

              EXTREMELY DELICATE 'SETTING PROJECTS'.

 When you are drilling claws with your "156C" bur for these projects. I suggest you use a new bur that has sharp teeth. This bur must have only one chance in 'drilling a seat' for each stone. Use your 10x loupe to examine the freshly drilled claws.  

The 'Halo' of claws needed for this ring must be using the newest bur that you can find. If your bur is well-worn, please don't use it. There is only one chance in drilling these mini-claws.

 These 'joined, or shared' claws are the best example of using the correct size of burs. 

  Selecting the correct size of bur depends on the size of the stone. Angle your bur just to clean out the inside of the claw setting. All of the bur cutting must use a sharp bur and not if the bur is well-worn. 

  In this photo, I used a bur that is almost the same size as the stone. The reason is that I will have the near exact cutting angle as of the stone.

 You can notice the cutting action taking place with the bur.

 I hope that this essay will guide you in selecting the correct size and angle of 156C bur.